Method for treating tissue in arthroscopic environment

ABSTRACT

A method for treating tissue having a surface in an arthroscopic environment of a mammalian body having a body temperature with a probe having a proximal end and an electrode at a distal end. The method includes the steps of providing a warmed irrigating solution having a temperature approximating the body temperature, delivering the warmed irrigating solution into the arthroscopic environment, introducing the distal extremity of the probe into the arthroscopic environment, positioning the electrode adjacent the surface of the tissue and supplying thermal energy to the electrode so as to treat the tissue. The warmed irrigating solution inhibits undesirable heating below the surface of the tissue.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a new and improved method for treatingtissue in an arthroscopic environment of a mammalian body.

[0003] 2. Description of Related Art

[0004] The normal function of joints in humans depends on thedistribution of relatively large forces across the body surfaces. Indiarthrodial joints, the magnitude of the joint forces reaches levelsfour to seven times body weight. These forces are dispersed by articularcartilage in the joint. Proper cartilage function occurs via a highlyorganized extracellular matrix maintaining a fixed charge density andpossessing a high affinity for water.

[0005] Chondromalacia occurs when cartilage beds in joints become wornand degenerate into strands of cartilage which extend away from theirrespective cartilage beds and into the joint cavity. The cartilagesurface becomes visibly disrupted, fissured and fibrillated. The damagedcartilage has deleterious effects on the mechanical properties andnormal function of articular surface. The fibrillated cartilage maybreakdown and break off to form particulate matter. It is theparticulate matter (broken fibrils) and various proteins and enzymesreleased when the normally smooth layered architecture of cartilage isundermined and frayed, which causes pain by irritating the synoviallining of the joint.

[0006] Treatment to date has included surgical intervention. In onearthroscopic procedure, a shaver is introduced through an arthroscopeand is used to mechanically remove the strands of disrupted andfibrillated cartilage. However, this treatment can disrupt and removepart of the normal healthy cartilage bed and does not restore a smoothsurface nor improve the mechanical function. In fact, mechanical shavinghas several drawbacks including: 1) adjacent normal cartilage is oftenremoved while debriding focal lesions; 2) it is difficult to completelysmooth the cartilage surface and not leave fine fibrillated regions; and3) it is a challenge to create a completely smooth cartilage surfacewith mechanical shaving. After treatment, normal loading typicallycauses continued degradation that results in further fibrillation anddegradation.

[0007] By way of example, the thickness of articular cartilage in theregion of the femoral condyles is approximately 2-4 mm in humans.Traditional mechanical debridement with shaving systems usually removes200-400 μm of cartilage including diseased cartilage and underlyingnormal cartilage if the shaver is well controlled during the treatment.Following mechanical debridement, further chondrocyte death between100-400 μm deep to the surface occurs within the first two weeks ofsurgery. Therefore, mechanical debridement with a shaver results in300-800 μm of chondrocyte loss, due to tissue removal and subsequentchondrocyte death with the cartilaginous surface still microscopicallyrough following treatment.

[0008] Another modality for the repair and treatment of the damagedcartilage includes open procedures which can lead to increased recoverytime and a possible increase in pain and further dysfunction of thejoint.

[0009] The use of thermal chondroplasty for treating cartilage jointsurfaces is known and thermal chondroplasty with radiofrequency energy(RFE) has gained widespread use over the past several years. Studieshave shown that RFE treatment results in smoother cartilage surfacesthan conventional mechanical debridement. Currently, there are two basicRFE systems available for clinical application, monopolar RFE (mRFE) andbipolar RFE (bRFE) systems. In addition, temperature controlled RFEprobes and generators are available for clinical application with bothmonopolar and bipolar RFE systems.

[0010] An exemplary device for treating fibrillated cartilage jointsurfaces or irregular cartilage joint surfaces in an arthroscopicprocedure which delivers sufficient RFE to reduce the level offibrillation of the cartilage joint surface is described in U.S. Pat.No. 6,068,628 to Fanton et al. Particular care is used to minimize anyundesired thermal effect on non-targeted tissue and thereby preventnecrosis below the surface of the cartilage joint surface into thehealthy layer since cartilage does not grow and regenerate after beingdamaged.

[0011] Generally, when an arthroscopic procedure utilizes thermalenergy, lavage is often used in order to distend the joint cavity and toflush and debris from the joint cavity which is generated during theprocedure. Generally, room-temperature lavage is used, however, a trendto use cooled lavage has recently developed. Although usingroom-temperature and/or cooled lavage is acceptable and generallybeneficial for some procedures, during other procedures such lavage mayhave an undesired cooling effect. In particular, when using atemperature controlled probe having a feedback controller, the feedbackcontroller may cause the probe to overcompensate and actually delivermore energy than is necessary, resulting in deleterious effects onchondrocyte viability.

[0012] In view of the foregoing, it would be desirable to provide amethod for treating tissue in an arthroscopic environment, for example,to coagulate fibrillated cartilage strands together, without undesirablecooling within the arthroscopic environment which may, in some cases,cause significant chondrocyte death during RFE treatment for thermalchondroplasty.

SUMMARY OF THE INVENTION

[0013] In summary, one aspect of the present invention is directed to amethod for treating tissue having a surface in an arthroscopicenvironment of a mammalian body having a body temperature with a probehaving a proximal end and an electrode at a distal end. The methodincludes the steps of providing a warmed irrigating solution having atemperature approximating the body temperature, delivering the warmedirrigating solution into the arthroscopic environment, introducing thedistal extremity of the probe into the arthroscopic environment,positioning the electrode adjacent the surface of the tissue andsupplying thermal energy to the electrode so as to treat the tissue. Thewarmed irrigating solution inhibits undesirable heating below thesurface of the tissue.

[0014] In general, one advantage of the present invention is to providea method for delivering energy within a arthroscopic environment to atargeted tissue surface while minimizing undesirable heating below thesurface of the tissue.

[0015] Another advantage of the present invention is provide a methodfor delivering energy to articular cartilage and particularlyfibrillated articular cartilage, for treatment thereof, while minimizingcollateral thermal effect on non-targeted portions and/or depths of thecartilage.

[0016] A further advantage of the present invention is to provide amethod that can be practiced with a temperature controlledelectrosurgical probe for minimizing and controlling chondrocyte deathand improving safety.

[0017] Another advantage of the present invention is to provide a methodof the above character in which sufficient thermal energy can bedelivered to coagulate cartilage fibrils in predictable and reproduciblelevels thereby minimizing collateral damage when using atemperature-controlled device.

[0018] Yet another advantage of the present invention is to provide amethod of the above character which can be used for treatingchondromalacia and other articular cartilage defects.

[0019] The method for treating tissue of the present invention has otherfeatures and advantages which will be apparent from or are set forth inmore detail in the accompanying drawings, which are incorporated in andform a part of this specification, and the following DetailedDescription of the Invention, which together serve to explain theprinciples of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is schematic view of a system incorporating an apparatusfor treatment of fibrillated tissue in use on a knee of a human body.

[0021]FIG. 2 is an enlarged schematic view of a knee capsule beingtreated by the system shown in FIG. 1.

[0022]FIG. 3 is an enlarged perspective view of an end of the apparatusshown in FIG. 1 treating a section of fibrillated tissue.

[0023]FIG. 4 is a graphic illustrating scanning electron microscopy(SEM) scores of a monopolar radio frequency energy (mRFE) treatedsurface at different lavage temperature/treatment time combinations.

[0024]FIG. 5 is an enlarged perspective view of an end of anotherapparatus which can be incorporated in the system of FIG. 1 fortreatment of fibrillated tissue in use on a knee of a human body.

[0025]FIG. 6 is a cross-section view of the apparatus of FIG. 5 takenalong line 6-6 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Reference will now be made in detail to the preferred embodimentsof the invention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to those embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims.

[0027] Turning now to the drawings, wherein like components aredesignated by like reference numerals throughout the various figures,attention is directed to FIGS. 1 and 2 which illustrate a system 30 withwhich the method for treating tissue in an arthroscopic environment of amammalian body utilizing normothermic irrigating solution, that is,irrigating solution warmed to the normal body temperature of themammalian body, can be performed in accordance with the presentinvention.

[0028] System 30 incorporates an irrigant source 31, an irrigantcollection 32, a cathode ray tube or video display unit 36, and anapparatus 37 for treating a joint of a mammalian body. An exemplary kneejoint 38 connecting a thigh 41 and a shin 42 is shown in FIGS. 1 and 2.Knee joint 38 is the junction of three bones, namely a thigh bone orfemur 43, a shin bone or tibia 47, and a kneecap or patella (not shown).The ends of femur 43, tibia 47, and the patella are covered witharticular cartilage 48 and are located within a joint capsule 49.

[0029] As shown in FIG. 3, cartilage or cartilage fibrils 52 may extendfrom a respective cartilage bed 53 for a length of approximately one toten millimeters and often extend approximately four to sevenmillimeters. Disrupted articular cartilage 48 can further includefissures 54 and fragmented, avulsed or frayed cartilage. Hence, forpurposes of the disclosure, disrupted articular cartilage 48 is broadenough to include cartilage that is fibrillated, fragmented and/orfissured.

[0030] The method of the present invention can be performed using thedisclosed apparatus in combination with other standard arthroscopicimplements such as an irrigating system, a viewing system and apositioning system in addition to the otherwise conventional equipmentutilized in a minimally invasive procedure conducted on a mammal undergeneral anesthesia. For example, a standard arthroscopic system such asthe ones described in U.S. Pat. No. 6,068,628, the entire contents ofwhich are incorporated herein by this reference, can be utilized foraccess to the joint capsule. Similarly, another arthroscopic systemwhich can be utilized for access to the joint capsule is described inU.S. patent application Se. No. ______ [Attorney Docket No.A-69458/ENB/VEJ], filed Feb. 8, 2001 and entitled Method and Apparatusfor Treatment of Disrupted Articular Cartilage, the entire contents ofwhich are incorporated herein by this reference.

[0031] Turning now to the irrigating system, any suitable irrigantsource can be utilized, such as solution bags (not shown) of normal orisotonic saline. In accordance with the present invention, the irrigantsource provides normothermic irrigating solution, that is, solutionwhich has been warmed to a temperature approximating the bodytemperature of the mammalian body upon which the method of the presentinvention is performed. In one embodiment, irrigating solution which iswarmed to approximately 37° C., the body temperature of a human, isprovided as a lavage for joint capsule 49. One should appreciate thatthe normothermic temperature may vary depending upon what type of mammalthe method of the present invention is performed. The solution can bewarmed to body temperature by placing bags of solution in a tissue bath,by a heat/stir plate device, or other means known in the art. In orderto monitor temperature of the solution, a strip thermometer 63, whichthermometer reads a different color depending upon the temperaturesensed, or other well known means can be mounted on the bags of solutionand/or solution source 31. For example, to ensure that irrigatingsolution is at the proper temperature, a bag of solution can be placedinto a tissue bath for approximately 45 minutes to approximately onehour and/or until the thermometer indicates that the solution is theproper temperature.

[0032] An irrigating connection tube 64 includes tubing clamps or othersuitable means for mechanically inhibiting and controlling the flow ofthe irrigating solution. A first percutaneous cannula 65 provides aportal for introducing irrigant into joint capsule 49 adjacent articularcartilage 48, as illustrated in FIGS. 1 and 2. A second cannula 66provides a second portal or outflow port allowing irrigating fluid toexit joint capsule 49. Cannula 66 optionally includes a diversion tube67 to direct the outflow of the irrigant away from an operator. Oneshould appreciate that the irrigating system optionally may include apump system that senses intra-articular pressure and maintains a desiredpressure within joint capsule 49 to insure distension of the joint andadequate hemostasis. Alternatively, intra-articular pressure can begenerated in a well known manner by elevating the solution bags abovethe level of the patient making use of a simple gravity supply.

[0033] Either one or both of cannulas 65 and 66 may be incorporated intoa cannula system allowing the introduction of an arthroscopic scope 68for viewing the interior of joint capsule 49 and distal extremity 71 bof probe member 71, as well as other interventional tools includingother probes, cutting tools, electrosurgical instruments andelectrothermal instruments which may be introduced into joint capsule49. Arthroscopic scope 68 generally includes an optical rod lens whichoptionally is operably connected to a video camera that provides a videosignal to a suitable display unit 36, such as a cathode ray tube, aliquid crystal display or a plasma monitor, for viewing by the operator.

[0034] Referring to FIGS. 1 and 2, apparatus 37 generally includes anelongate probe member 71 having a proximal extremity 71 a and a distalextremity 71 b. A probe handle 72 is mounted to proximal extremity 71 aand an active electrode 73 (shown in FIG. 3) is provided on distalextremity 71 b. One should appreciate that other probes can be used inaccordance with the present invention. For example, other probes whichcan be utilized are described in U.S. patent application Ser. No. ______[Attorney Docket No. A-69458/ENB/VEJ], filed Feb. 8, 2001 and entitledMethod and Apparatus for Treatment of Disrupted Articular Cartilage, theentire contents of which are incorporated herein by this reference.

[0035] In one embodiment, probe member 71 includes an elongated andhollow outer shaft 74, as shown in FIG. 3. A peripheral wall 75 isformed by a distal extremity of outer shaft 74. Peripheral wall 75defines a cavity 76. A lower edge of peripheral wall 75 defines a distalopening 80 communicating with cavity 76. Although the illustratedperipheral wall 75 is tubular, one should appreciate that it may takeother forms. For example, the peripheral wall may be oval or polygonalin shape.

[0036] Active electrode 73 is made from any suitable conductive materialsuch as stainless steel, platinum, iridium, titanium, silver and theiralloys or any other medical grade metal. In the embodiment shown in FIG.3, the electrode 73 has an outer surface having a convex and anoutwardly bowed shape. It should be appreciated, however, that the outersurface of active electrode 73 can be planar, convex, or of any othersuitable shape and be within the scope of the present invention.

[0037] Distal extremity 71 b of probe member 71 includes an inner shaft81 which is affixed to outer shaft 74 by a one or more brackets orspacers 82, as shown in FIG. 3. Conductive lead means is included withinner shaft 81 for providing energy to active electrode 73. Suchconductive lead means can be in the form of a tubular member or tube,for example, inner shaft 81. Such conductive lead means can be made fromany suitable conductive material and preferably a suitable medical gradeconductor such as stainless steel 304 or any other stainless steel,MP35N, alloy metals, noble metals, any other suitable conductive carbonmaterial or imbedded plastics or polymers. Active electrode 73 issecured to the distal end of inner shaft 81 by any suitable means so asto be electrically coupled to the active electrode. An additionaltubular member or outer side wall, preferably in the form of a sleeve,is shrunk about or otherwise suitably disposed around the outside ofinner shaft 81 and the side wall of the active electrode 73. Such asleeve is preferably formed from a thermally-insulating material and ismore preferably formed from TEFLON® (PTFE), polyolefin or nylon (PFA) orother plastics or polymers, serves to thermally insulate the side wallof active electrode 73 and electrode conductive inner shaft 81.

[0038] Spacers 82 are circumferentially disposed about the inner shaft81 and serve to space active electrode 73 and the inner shaft 81radially within outer shaft 74. The spacers 82 can be made from anysuitable material such as glass, ceramic or any nonconductive electricaland/or thermal material. In one embodiment, active electrode 73 isspaced inwardly or proximally from opening 80 a distance ofapproximately two to ten millimeters and preferably approximately two tofive millimeters so as to be recessed within distal extremity 71 b. Oneshould appreciate, however, that the method of the present invention maybe performed using other types of probes, including probes having anactive electrode that is not spaced from the opening.

[0039] A temperature or heat sensor 84 is preferentially carried bydistal extremity 71 b for measuring and monitoring the temperature ofactive electrode 73. Heat sensor 84 is of a conventional design and mayconsist of a thermocouple, a thermistor, a resistive wire, an integratedcircuit (IC) or any other suitable sensor. The sensor 84 is electricallycoupled to active electrode 73. Although sensor 84 of the illustratedembodiment is located within inner shaft 81 adjacent active electrode73, one should appreciate that the heat sensor can be provided elsewhereprovided that the heat sensor is capable of monitoring ambienttemperature in the vicinity of the active electrode..

[0040] System 30 of the present invention is an electrothermal systemwhich includes probe apparatus 37 and an energy source 85 to thermallycoagulate disrupted articular cartilage, for example a fibrillatedarticular surface typically present in Grades I, II and IIIchondromalacia. Energy source 85 is preferably a radiofrequency (RF)generator and controller hereinafter referred to as RF generator 85. RFgenerator 85 includes a feedback controller which is dependent upontemperature and/or impedance. Active electrode 73 is electricallyconnected to RF generator 85 by means of conductive inner shaft 81 and asuitable connecting cable 86, which extends from the energy source 85 toprobe handle 72 in order to electrically couple to the proximal end ofinner shaft 81. As shown in FIG. 1, connecting cable 86 may beintegrated to the probe handle 72 to form a one-piece unit betweenapparatus 37 and probe handle 72. This provides a fluid resistantenvironment within electrosurgical probe handle 72 to prevent electricaldisconnects and shorting between apparatus 37 and energy source 85. Itwill also be appreciated that probe handle 72 and connecting cable 86may also be separate units utilizing a keyed and/or electricallyinsulated connection at a proximal end of probe handle 72.

[0041] In one embodiment, a grounding pad 87 is provided on thigh 41 ofa patient's body as shown in FIG. 1. The grounding pad 87 may also beplaced on any electrically suitable location of the body to complete thecircuit. Grounding pad 87 is electrically connected to radio frequencygenerator 85 via a second return connecting cable 91 to complete theelectrical circuit. RF generator 85 can deliver high frequency orradiofrequency voltage in the range of one to 350 watts.

[0042] Optionally, impedance is monitored by energy source 85 along theelectrical circuit between power output and return input of the energysource 85. The energy source 85 monitors the impedance of the electricalcircuit by measuring the difference between the output power and theinput return as a function of voltage over current. In a typicalmonopolar system the impedance level is about 100 ohms and in a typicalbipolar system the impedance level is about 60 ohms.

[0043] The feedback controller of RF generator 85 monitors thetemperature of the tissue or cartilage being treated by monitoring thetemperature experienced by sensor 84 located in the proximity of activeelectrode 73. The feedback controller compares such temperature to aprogrammed temperature profile. The feedback control can also directlymonitor system impedance of the electrical circuit. If the measuredimpedance exceeds a predetermined level, energy delivery to activeelectrode 73 is disabled or adjusted thus ceasing or adjusting deliveryof thermal energy to active electrode 73. If the temperature withincavity 76 measured by sensor 84 exceeds a predetermined desiredtemperature, energy delivery to active electrode 73 is disabled oradjusted thus ceasing or adjusting delivery of thermal energy to activeelectrode 73.

[0044] Optionally, apparatus 37 may be used in combination with asuction source. For example, the probe member includes a lumen 92, asshown in FIG. 3, which extends from cavity 76 towards proximal extremity71 a (not shown in FIG. 3) of the probe member and through probe handle72. In the illustrated embodiment, lumen 92 is annular in cross sectionat distal extremity 71 b where the lumen communicates with cavity 76.Specifically, such annular lumen 92 is formed at its outside byperipheral wall 75 and at its inside by inner shaft 81. Lumen 92 fluidlyconnects with the suction source via a suitable fluid coupling adjacentproximal extremity 71 a in a conventional manner. In such configuration,the suction source can be activated to produce a suction effect withinlumen 92 and cavity 76. The suction source can be activated by aphysician to aspirate the joint cavity as desired by the physician. Whenthe suction source is activated, fluid, particulates and other matterwithin the surgical field is aspirated into a collection vessel, forexample, irrigant collection 32. One should appreciate, however, thatapparatus 37 may be used with or without a suction source.

[0045] In operation and use, a suitable positioning system can be usedto immobilize joint 38 to facilitate the operator's or physician'saccess to joint capsule 49. The positioning system is selected basedupon the specific anatomy to be addressed with the procedure inaccordance with the present invention.

[0046] After the patient has been appropriately sedated or anesthetized,joint capsule 49 is pressurized by a suitable irrigant to create a workarea within the joint space 49, as shown in FIG. 2. For example, fluidinflow from irrigant source 31 by means of pump and/or gravityintroduces pressurized irrigant fluid into joint capsule 49 so as tocreate a workspace within joint capsule 49 as well as to provide aflushing and a warming, temperature stabilizing effect.

[0047] In contrast to prior methods in which the irrigating solutionsare commonly stored in the operating room and are then used at roomtemperature, that is approximately 19°-22° C., the irrigating solutionis pre-warmed to a temperature approximating the body temperature of themammalian body upon which the method of the present invention ispracticed. The saline or other irrigating fluid from irrigant source 31further serves to stabilize the temperature of cartilage bed 53 andsurrounding tissue within joint capsule 49.

[0048] Probe handle 72 is grasped by the physician to introduce distalextremity 71 b of probe member 71 through cannula 66 and into the jointcapsule of the patient and thereafter to position lower edge 56 ofdistal extremity 71 b adjacent disrupted articular cartilage 48.Although distal extremity 71 b is shown to be substantially flushagainst articular cartilage 48, one should appreciate that the actualplacement of the probe member with respect to the articular cartilagewill depend upon the actual probe member used. Scope 68 allows thephysician to view distal extremity 71 b within joint capsule 49 and thusfacilitates movement of distal extremity 71 b relative to articularcartilage bed 53 by the physician.

[0049] Probe member 71, namely distal extremity 71 a, is swept acrossthe surface of articular cartilage bed 53. The physician activates RFgenerator 85 and RFE is supplied to active electrode 73. The salineand/or other conductive irrigants present within joint capsule 49 serveto transmit such RFE and, together with other tissue of the mammalianbody, transmit the RFE to grounding pad 87. The passing of such radiofrequency through the fluid heats such fluid to a temperature that canbe monitored by temperature sensor 84. The amount of energy supplied toelectrode 73 controls the temperature of the electrode.

[0050] The disrupted articular cartilage which is immediately adjacentactive electrode 73, for example, the fibrillated articular cartilagefibrils or strands 52 extending from cartilage bed 53 over which cavity76 rests, are thermally treated by the heated fluid within cavity 76 soas to become coagulated cartilage. Fibrillated strands 52 which contactdistal surface 38 of active electrode 73 are similarly coagulated ormelded and thus treated. Subjecting the fibrillated articular cartilagestrands 52 to temperatures in the range of approximately 45° C. to 100°C., preferably in the range of approximately 45° C. to 85° C., and morepreferably in the range of approximately 45° C. to 60° C., causes thefibrillated articular cartilage strands 52 to meld into cartilage bed 53and thus form a substantially smooth coagulated mass on the surface ofthe cartilage bed 53 as indicated by numeral 93 in FIG. 3. In thismanner, the cartilage bed 53 is sealed into a coagulated mass 93. Thetreatment of disrupted articular cartilage 48 by apparatus 37 in theforegoing manner can also result in the sealing of fissures 54, one ofsuch sealed fissures 54 being shown by a dashed line in FIG. 3, and thesealing of any fragmented, avulsed or otherwise disrupted cartilage intoa coagulated mass 93.

[0051] In the illustrated embodiment, active electrode 73 is spaced orrecessed inwardly from opening 80 so as to minimize direct contactbetween the active electrode and cartilage bed 53 when apparatus 37 isutilized for treating fibrillated articular cartilage strands 52. Activeelectrode 73 is recessed within opening 80 a distance that allows forthe targeted fibrillated articular cartilage strands 52 to extend intothe cavity or space created by the extension of peripheral wall 75beyond distal surface 38 of the active electrode. The distance betweenthe active electrode and the surface of the articular cartilage bed 53is preferably such that the delivery of energy from RF generator 85coagulates the fibrillated articular cartilage strands into a coalescedand singular mass to form a contiguous articular cartilage surface. Suchdistance reduces the delivery of thermal energy to underlyingsubchondral bone thus preventing avascular necrosis (AVN). The movementof apparatus 37 by the operating physician across the disruptedarticular cartilage 48 limits the time of exposure of such cartilage tothermal heating, which is also a factor in preventing AVN. As notedabove, the active electrode need not be spaced from opening to fallwithin the scope of the present invention.

[0052] As thermal energy is so delivered to active electrode 73, thephysician advances or sweeps probe member 71 continuously acrosscartilage bed 53 at a speed that allows for sufficient coagulation offibrillated articular cartilage strands 52 to occur and form acoagulated mass 93, as shown in FIG. 3, but without excessive thermalexposure to deeper viable tissues including cartilage bed 53 andsubchondral bone such as tibia 47 (FIG. 2). The sweeping motion of theprobe member along cartilage bed 53 results in a convective thermaleffect that follows the path of the probe.

[0053] One should appreciate that tissues do not immediately heat upwhen exposed to thermal energy. The exposure time of thermal energy uponan area of cartilage bed 53 is a factor in treatment effectiveness. Thephenomena known as thermal latency of tissues determines the thermalresponse time, or thermal conduction time of the targeted tissue beingtreated. In accordance with the present invention, the use ofnormothermic irrigating solution reduces the effects of thermal latencybecause the temperature differential is reduced. In particular, thetemperature differential between ambient temperature and treatmenttemperature when normothermic irrigating solution is used is less thenthe temperature differential when room temperature or precooledirrigating solutions are used.

[0054] Temperature sensor 84 permits the ambient temperature of jointcapsule 49 to be accurately monitored. Accordingly, the temperature ofelectrode 73 can be accurately monitored and regulated therebyminimizing the possibility of thermal damage to non-targeted tissue aswell as to apparatus 37. For example, because the temperature isaccurately monitored, predictable and reproducible levels of energy canbe delivered in order to effectively meld fibrillated articularcartilage strands 52 and minimize collateral thermal effect onnon-targeted tissue including underlying cartilage bed 53 andsubchondral bone 47.

[0055] Advantageously, using a warmed irrigating solution, for example,a warmed lavage having a temperature approximating the body temperatureof the mammalian body to be treated can significantly decrease the depthof chondrocyte death. As noted above, warmed irrigating solution servesto stabilize the temperature of cartilage bed 53 and surrounding tissuewithin joint capsule 49. Such temperature stabilization advantageouslyminimizes the thermal heating of the deeper layers of cartilage bed 53and thus inhibits the undesirable thermal damage of such deeper tissues,as is demonstrated in the following exemplary study. The studydetermined that normothermic lavage solution, that is, lavage solutionwarmed to the normal body temperature of the body to the treated, limitsthe depth of chondrocyte death when a temperature controlled monopolarRFE (mRFE) treatment was used to perform thermal chondroplasty ascompared to room temperature lavage solution, that is, approximately 22°C. In the case of a treating a human body, the normothermia lavagesolution is warmed to approximately 37° C.

[0056] In the exemplary study, sixteen fresh osteochondral sections fromsixteen patients undergoing total or partial knee arthroplasty were usedto complete the study. Chondromalacia was graded using a modifiedOuterbridge system in which softened cartilage surface is designated as“Grade 1”, softened cartilage with fine fibrillations as “Grade 2”,fibrillated surface with pitting to subchondral bone as “Grade 3”, andfibrillation of cartilage and exposed subchondral bone as “Grade 4”. Toavoid experimental bias, each graded osteochondral section was cut intotwo sections. One section was treated with monopolar radiofrequencyenergy (mRFE) in physiologic saline (0.15M) at 22° C. (room temperature)whereas another section was treated in physiologic saline (0.15M) at 37°C. An area 2 cm distant from the radiofrequency energy (RFE) treatedarea on each specimen served as control.

[0057] For 37° C. lavage solution, 1 liter of physiologic saline wasplaced in a plastic container heated by a NUOVA II hot plate and stirrer(Thermolyne Corporation, Dubuque, Iowa, USA). A thermometer was used tomonitor the temperature, and the saline was maintained at 37° C. for 60minutes. After temperature stabilization, cartilage sections were placedin the saline and allowed to equilibrate for 20 minutes so that sectionsreached 37° C. prior to mRFE treatment. No fluid flow was used duringmRFE treatment based on the results from a previous study thatdetermined the negative effect of irrigation fluid flow on cartilagematrix temperatures during mRFE chondroplasty. A Vulcan EAS™ coupledwith a TAC-C II probe (Oratec Interventions, Inc, Menlo Park, Calif.)was used to deliver mRFE in a light contact fashion over a 1.0-cm² areaon each section in a paintbrush treatment pattern at a generator settingof 70° C. and 15 watts. RFE treatment times of 10 sec and 15 sec wereevaluated in the study. For each treatment time/lavage temperaturecombination, eight sections were tested (total, 32 treatments, 4 groups,n=8). Ten and 15 second treatment times were selected.

[0058] After RFE treatment, each treated area was processed for analysisby vital cell staining/confocal laser microscopy (CLM) and scanningelectron microscopy (SEM). A diamond-wafering blade (ISOMET® 2000Precision Saw; Buehler LTD. Corporation, Lake Bluff, Ill., U.S.A.) wasused to cut 1.5-mm thick osteochondral sections for CLM. Phosphatebuffered saline (PBS) was used for irrigation to avoid thermal injuryduring sectioning as previously described. Sections were placed in1.0-ml PBS and maintained at 4° C. for 3 hours prior to staining forcell viability.

[0059] Cell viability staining was performed using ethidium homodimer(EthD-1) and (acetoxymethylester) calcein-AM in conjunction with CLM.The 1.5-mm sections were stained by incubation in 1.0-ml of PBScontaining 1.0-mL calcein-AM per 10-mL EthD-1 (LIVE/DEAD®Viability/Cytotoxicity Kit (L-3224), Molecular Probes, Eugene, Oreg.)for 30 minutes at room temperature. The 1.5-mm osteochondral section wasplaced on a glass slide, moistened with several drops of PBS. A confocallaser microscope (BIO-RAD® MRC-1000, Bio-Rad, Hemel Hampstead/Cambridge,England) equipped with an argon laser and necessary filter systems(fluorescein and rhodamine) was used with a triple labeling technique.In this technique, the signals emitted from the double-stained specimenscan be distinguished because of their different absorption and emissionspectra These images are displayed on a monitor in a RGB (red, green andblue) mode. All cartilage samples were coded so that treatment time andlavage solution temperature were unknown to the examiners.

[0060] The depth of chondrocyte death of each section was determined foreach RFE treated region in the CLM image, and all images coded toprevent identification of the lavage temperature and treatment timeapplied. The CLM was calibrated using a micrometer measured through theobjective lens (2×) used for this project (20×total magnification;objective +eyepiece magnification). The pixel length measured on imageswas converted to micrometers as previously described. The depth ofchondrocyte death was determined for each confocal image of theosteochondral sections with Adobe PhotoShop™ (Adobe PhotoShop, Version5.5, San Jose, Calif.).

[0061] After evaluation by CLM, the same cartilage specimens weretrimmed (4×3×1.5 mm) and fixed in modified Kamovsky's solution (2%glutaraldehyde in 0.1 mol/L sodium cacodylate buffer, pH 7.4) for 2hours and then washed in 0.1 mol/L sodium cacodylate buffer twice atroom temperature. These samples were stored in 0.1 mol/L sodium PBS for8 hours at 4° C. After dehydration in a graded series of ethanol (50%,70%, 80%, and 100%) and air drying, the samples were coated with gold ina Bio-Rad E5000M gold coater and examined with a Hitachi S570 scanningelectron microscope. The image of each section was coded so that thelavage temperature and treatment time were unknown. The SEM images werescored by three investigators independently with a custom designedscoring system as previous study described. Higher scores indicate asmoother cartilage surface.

[0062] Mean depth of chondrocyte death, mean mRFE delivery power, timeto reach RFE preset temperature, and mean mRFE treatment temperature(temperature measured from thermocouple located within the RF probe tip)were compared among groups of lavage temperatures and treatment timecombinations using ANOVA (SAS version 7.1, SAS Institute, Cary, N.C.,USA). Factors included in the analysis were patient, treatment time, andlavage solution temperature. When differences among groups weredemonstrated by ANOVA, appropriate post hoc tests were employed. Pairedt-tests were used to compare the effect of lavage solution temperaturewithin treatment time groups. Patient gender was compared using Wilcoxonsign rank tests. The inter- and intra-observer precision errors weredetermined for the SEM scores. The Kruskal-Wallis test was used tocompare the SEM image scores between different lavage temperatures atthe same treatment time. When significance was identified using theKruskal-Wallis test, the Mann-Whitney procedure was used to compare thesubjective scores between groups. P-values less than 0.05 wereconsidered significant.

[0063] The results of the above study indicated that there were nosignificant differences in age or gender among treatment groups (meanage, 65±7 years; 7 males and 9 females; p>0.05).

[0064] CLM demonstrated that the depth of chondrocyte death in 37° C.lavage solution was significantly less than that in 22° C. solution atboth 10 and 15 sec treatment times (FIG. 1, Table 1). SEM demonstratedthat cartilage surfaces were smoothed in both 37° C. and 22° C. lavagesolutions treated for both 10 sec and 15 sec treatment times comparedwith the control specimens.

[0065] SEM demonstrated that chondromalacic cartilage surfaces treatedby RFE in 37° C. lavage solution were smoother than those treated in 22°C. solution for 10 sec (p<0.05), but that there were no differences insurface smoothing between sections treated in 37° C. and 22° C. lavagesolution for 15 sec treatment, as shown in FIG. 4. Higher scoresindicate smoother surface, as indicated by the vertical arrow. Scorevalues represent the means of three observers±standard deviation. Meanswith different letters are significantly different from each other atdifferent RFE treatment time intervals (p<0.05). Means with asterisk aresignificantly different from each other at different lavage temperatures(p<0.05). Scores above transverse line at score 2 mean that cartilagesurfaces were smoothed.

[0066] As shown in FIG. 4, chondromalacic cartilage surfaces treated byRFE for 15 sec were smoother than those treated for 10 sec treatmenttime group in both 37° C. and 22° C. lavage solutions (p<0.05). Theintra- and inter-observer precision errors for SEM scores were 10.8% and12.9% respectively.

[0067] The mean mRFE treatment temperatures in 37° C. lavage solutionwas higher than in 22° C. lavage solution for both 10 sec and 15 sectreatment times (p<0.05), whereas RFE delivery power in 37° C. was lowerthan 22° C. lavage solution for both treatment times (p<0.05). TABLE 1The Effects of Lavage Temperature^(Ψ) Treatment Time 10 sec 15 secLavage temp (° C.) 22 37 22 37 Depth of 620 ± 106 420* ± 219 930 ± 236590* ± 214 chondrocyte death (μm) Mean power 8.5 ± 0.6 5.9* ± 0.9 7.6 ±0.8 5.1* ± 0.4 (watts) Time to set 1.8 ± 0.5 0.7* ± 0.2 1.3 ± 0.5 1.0* ±0.5 temp (sec) Mean probe 67.5 ± 1.1  70.1* ± 0.8  68.7 ± 0.6  70.3* ±0.4  temp (° C.)

[0068] The times for mRFE to reach preset temperature were faster in 37°C. lavage solution than in 22° C. lavage solution for both 10 sec and 15sec mRFE treatment times (p<0.05). mRFE treatment temperatures were morestable in 37° C. lavage solution (coefficient of variation (CV)=6.23%)compared to 22° C. lavage solution (CV=7.92%) (p<0.05).

[0069] Thermal chondroplasty performed with mRFE in 37° C. lavagesolution caused significantly less chondrocyte death than in 22° C.lavage solution. Increasing the lavage solution temperature allowed theprobe tip to reach preset temperature more rapidly and resulted in lesstotal power (energy) delivery while still effectively smoothing thecartilaginous surface.

[0070] The goal of this study was to determine if normothermic lavagesolution (37° C.) would limit the depth of chondrocyte death whentemperature controlled mRFE was used to perform thermal chondroplastycompared to room temperature lavage solution (22° C.). This hypothesiswas based on the mRFE's design and temperature control algorithm. ThemRFE system evaluated (Vulcan EAS™ RF generator, Oratec Interventions,Inc, Menlo Park, Calif.) uses delivered power to control the tissuetemperature reflected by a thermocouple within the mRFE probe tip. Atthe beginning of treatment, the RF generator delivers full preset powerto cause tissue heating. The thermocouple within the mRFE probe tip issubsequently heated, reaching the preset temperature relatively quickly.After reaching the preset temperature, the mRFE algorithm reduces thepower to decrease tissue/probe-tip temperature and then uses minimumpower output to maintain the tissue temperature near the presettemperature. This results in the mRFE generator delivering mean powersthat are significantly less than preset powers (34-57% of preset powerin this study) to maintain the preset temperatures.

[0071] The results of this study demonstrated that thermal chondroplastyperformed with mRFE in 37° C. lavage solution caused significantly lesschondrocyte death than that in 22° C. lavage solution. The explanationfor this decreased cell death is that less delivered power (energy)resulted in less chondrocyte injury. The delivered power in 37° C.lavage solution was approximately 40% less than that in 22° C. lavagesolution during both 10 and 15 sec treatment times. Delivered powerequals the electric current multiplied by electric voltage. Organ et al.reported that RFE current intensity (I) had a very strong influence onthe lesion generated. The lesion size increased as I². The temperaturecontrolled mRFE device tested in this study was able to maintain theprobe tip temperatures equivalent to preset temperature at lower meanpowers in 37° C. compared to 22° C. lavage solution.

[0072] In addition, the results of this study demonstrated that the timeto reach preset temperature at the initiation of treatment in 37° C.lavage solution was significantly faster than in 22° C. lavage solutionin both 10 and 15 sec treatment groups. This likely occurred because thetemperature difference between the lavage solution and RFE presettemperature was 33° C. for the 37° C. group and 48° C. for the 22° C.group.

[0073] In this study, SEM demonstrated that there were no significantdifferences in cartilage surface smoothing and contouring between the37° C. lavage solution and the 22° C. lavage solution for the 15 sectreatment time group. However, mRFE treatment of the cartilage surfacein 37° C. lavage solution for 10 sec resulted in a significantlysmoother surface than the same treatment time in 22° C. lavage solution.This probably was caused by the faster time to preset temperature in the37° C. lavage solution group (0.7 vs 1.8 sec) and the higher meantemperature reached with 37° C. group (70.1° C. vs 67.5° C.). The majorreason why mean mRFE treatment temperature in 37° C. lavage solution wassignificantly higher than that in 22° C. lavage solution during mRFEtreatment was that the temperature fluctuation in 37° C. lavage solutionwas less than in 22° C. lavage solution. The mRFE generator is able tomaintain probe tip temperature closer to the preset temperature in 37°C. lavage solution than in 22° C. lavage solution, with lower deliveredpower.

[0074] Advantageously, this ex vivo study indicated that thermalchondroplasty with mRFE using 37° C. lavage solution significantlyreduced chondrocyte death compared to using the standard roomtemperature (22° C.) lavage solution. During 10 and 15 sec treatmenttimes over a 1 cm² area of grade 2 chondromalacic cartilage, the meandepth of chondrocyte death ranged from 420-590 μm. This depth is similarto expected depth of chondrocyte loss produced by mechanical debridementand shaving. Compared to mechanical debridement with a shaver, mRFE hasseveral advantages: 1) a smoother surface may be produced, 2) injury toadjacent and untreated regions may be more easily avoided, and 3) rapidand easy contouring is achieved that may result in shortened operativeprocess.

[0075] In addition to the above advantages, the method for treatingtissue using normothermic lavage in accordance with the presentinvention minimizes undesirable heating below the surface of the tissuethereby resulting in less depth of chondrocyte death and producessmoother surfaces as compared to other methods using cooler lavages.Advantageously, the method of the present invention requires less energyto heat tissue, including articular cartilage to be treated, andrequires less power to maintain probe temperature. As less power isrequired to maintain probe temperature, thermal energy can be deliveredto the probe in predictable and reproducible levels in such a mannerthat the feedback controller is less likely to overcompensate inmaintaining probe temperature.

[0076] The structure of the apparatus and probe member with which thepresent method is utilized may vary widely and fall within the scope ofthe present invention. For example, the probe members may have a varietyof different geometric configurations. For example, the electrode may bespherical, flat, asymmetric or concave. In addition, it should beappreciated that the energy source, apparatus and method of the presentinvention can utilize other suitable frequencies along theelectromagnetic spectrum, including infrared, coherent light, sonic andmicrowave, for heating the disrupted articular cartilage exposed theretoand be within the scope of the present invention.

[0077] In another embodiment, and elongate probe member 96 as shown inFIGS. 5 and 6 is utilized instead of elongate probe member 71. Elongateprobe member 96 is similar to that shown in U.S. Pat. No. 6,068,628, theentire content of which is incorporated by this reference. A distalextremity 96 b of elongate probe member 96 includes first and secondannular electrodes 97 and 98 which are formed on a periphery of surfaces102 and 103, respectively. A temperature sensor 104, similar to heatsensor 84 discussed above, is provided on the distal extremity of probemember 96 to monitor ambient temperature adjacent the electrodes.

[0078] Probe member 96 can be operated in either a monopolar or abipolar mode. In particular, probe member 96 can be operated in abipolar mode as it includes an active electrode 97 and a returnelectrode 98 provided on an external surface surfaces 102 and 103.Similar to probe member 71, active electrode 97 is electricallyconnected to the RF generator 85. Return electrode 98 is alsoelectrically connected to the RF generator and competes the electricalcircuit therewith instead of a grounding pad. The bipolar current pathextends from active electrode 97 to return electrode 98 in a well knownmanner.

[0079] In use and operation, probe member 96 is used in substantiallythe same manner as probe member 71 to apply thermal energy to tissue inan arthroscopic environment. Similarly, the method of the presentinvention utilizing warmed irrigating solution can be practiced withprobe member 96 in substantially the same manner as probe member 71discussed above. One should appreciate that the method of the presentinvention can similarly be practiced using a wide variety of probemembers designed and configured to apply thermal energy to a tissue inan arthroscopic environment.

[0080] One method for treating tissue having a surface in anarthroscopic environment of a mammalian body having a body temperaturewith a probe having a proximal end and an electrode at a distal end inaccordance with the present invention includes the steps of providing awarmed irrigating solution having a temperature approximating the bodytemperature, delivering the warmed irrigating solution into thearthroscopic environment, introducing the distal extremity of the probeinto the arthroscopic environment, positioning the electrode adjacentthe surface of the tissue and supplying thermal energy to the electrodeso as to treat the tissue. The warmed irrigating solution inhibitsundesirable heating below the surface of the tissue.

[0081] The warmed irrigating solution may be selected from the groupconsisting of normal saline, ringers lactated solution, Glycine andbacteriostatic water. The warmed irrigating solution may have atemperature of approximately 37° C. and may be warmed by a tissue bath.

[0082] The method may further include the step of monitoring the ambienttemperature within the arthroscopic environment with a sensor carried bythe distal extremity of the probe.

[0083] The monitoring step may further include the step of modulatingthe amount of thermal energy supplied to the electrode in response tothe ambient temperature within the arthroscopic environment.

[0084] The supplying step may further include the step of supplyingradio frequency energy to the electrode. The supplying step may furtherinclude the step of supplying radio frequency energy between theelectrode and a return electrode, the electrode and the return electrodebeing coupled to a radio frequency generator. The return electrode maybe carried by the distal extremity of the probe.

[0085] The surface may be a fibrillated cartilage surface, in whichcase, the supplying step includes the step of supplying sufficientthermal energy to the electrode to reduce the level of fibrillation atthe fibrillated cartilage surface.

[0086] Another method for treating tissue having a surface in anarthroscopic environment of a mammalian body having a body temperaturewith a probe having a proximal end and an electrode at a distal end inaccordance with the present invention includes the steps of providing awarmed irrigating solution having a temperature approximating the bodytemperature, delivering the warmed irrigating solution into thearthroscopic environment, introducing the distal extremity of the probeinto the arthroscopic environment, positioning the electrode adjacentthe surface of the tissue, supplying radio frequency energy to theelectrode so as to treat the surface of the tissue whereby the warmedirrigating solution inhibits undesirable heating below the surface ofthe tissue and monitoring the temperature of the arthroscopicenvironment so as to modulate the supply of radio frequency energy tothe electrode in response to such monitored temperature.

[0087] The supplying step may further include the step of coupling theelectrode to a radio frequency generator. The supplying step may includethe step of coupling a return electrode to the radio frequency generatorso that the radio frequency energy passes between the electrode and thereturn electrode. The return electrode may be carried by the distalextremity of the probe.

[0088] The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the Claims appended hereto and theirequivalents.

What is claimed is:
 1. A method for treating tissue having a surface inan arthroscopic environment of a mammalian body having a bodytemperature with a probe having a proximal end and an electrode at adistal end, comprising the steps of providing a warmed irrigatingsolution having a temperature approximating the body temperature,delivering the warmed irrigating solution into the arthroscopicenvironment, introducing the distal extremity of the probe into thearthroscopic environment, positioning the electrode adjacent the surfaceof the tissue and supplying thermal energy to the electrode so as totreat the tissue whereby the warmed irrigating solution inhibitsundesirable heating below the surface of the tissue.
 2. The method ofclaim 1 wherein the warmed irrigating solution is selected from thegroup consisting of normal saline, ringers lactated solution, Glycineand bacteriostatic water.
 3. The method of claim 2 wherein the warmedirrigating solution has a temperature of approximately 37° C.
 4. Themethod of claim 1 wherein the providing step includes the step ofproviding an irrigation solution warmed by a tissue bath.
 5. The methodof claim 1 further comprising the step of monitoring the ambienttemperature within the arthroscopic environment.
 6. The method of claim5 wherein the monitoring step includes the step of monitoring theambient temperature within the arthroscopic environment with a sensorcarried by the distal extremity of the probe.
 7. The method of claim 5wherein the supplying step includes the step of modulating the amount ofthermal energy supplied to the electrode in response to the ambienttemperature within the arthroscopic environment.
 8. The method of claim1 wherein the supplying step includes the step of supplying radiofrequency energy to the electrode.
 9. The method claim 8 wherein thesupplying step includes the step of supplying radio frequency energybetween the electrode and a return electrode, the electrode and thereturn electrode being coupled to a radio frequency generator.
 10. Themethod of claim 9 wherein the return electrode is carried by the distalextremity of the probe.
 11. The method for claim 1 wherein the surfaceis a fibrillated cartilage surface, the supplying step includes the stepof supplying sufficient thermal energy to the electrode to reduce thelevel of fibrillation at the fibrillated cartilage surface.
 12. A methodfor treating tissue having a surface in an arthroscopic environment of amammalian body having a body temperature with a probe having a proximalend and a radio frequency electrode, comprising the steps of providing awarmed irrigating solution having a temperature approximating the bodytemperature, delivering the warmed irrigating solution into thearthroscopic environment, introducing the distal extremity of the probeinto the arthroscopic environment, positioning the electrode adjacentthe surface of the tissue, supplying radio frequency energy to theelectrode so as to treat the surface of the tissue whereby the warmedirrigating solution inhibits undesirable heating below the surface ofthe tissue and monitoring the temperature of the arthroscopicenvironment so as to modulate the supply of radio frequency energy tothe electrode in response to such monitored temperature.
 13. The methodof claim 12 wherein the supplying step includes the step of coupling theelectrode to a radio frequency generator.
 14. The method of claim 13wherein the supplying step includes the step of coupling a returnelectrode to the radio frequency generator so that the radio frequencyenergy passes between the electrode and the return electrode.
 15. Themethod of claim 14 wherein the return electrode is carried by the distalextremity of the probe.